1. Technical Field
The present invention relates generally to a reeling mechanism of a window covering, and more particularly to a damping device which is capable of slowing down the speed of raising and extending the window covering.
2. Description of Related Art
A conventional window covering includes a headrail, a covering material, and a rotary shaft, wherein the rotary shaft is provided in the headrail to raise and extend the covering material. During the process of extending the covering material, the weight of the covering material would generate a downward pulling force, which accelerates the rolling of the rotary shaft, and makes the covering material extend with an excessive speed. As a result, some components may be worn, or the covering material may bump into objects below. Similarly, during the process of raising the covering material, an excessive rolling speed of the rotary shaft would make the covering material raise too fast as well.
In light of this, a traditional window covering usually includes an oil damping device installed on a rotary shaft thereof to slow down the rotating speed of the rotary shaft and, consequently, the speed of raising or extending the covering material. However, the viscosity of the oil in the oil damping device is sensitive to temperature. When the temperature is high, the viscosity of the oil is low, which reduces the damping effect; in contrast, when the temperature is low, the viscosity of the oil is high, which affects the smoothness of operating the window covering. Also, after being used for a long period, the oil may leak from the oil damping device, which worsens the damping effect, and even makes the oil damping device completely unable to provide the damping effect.